A letter written by German physicist Albert Einstein in 1919, concerning the arrangement of divorce to his wife and the education of his children, has been sold for a whopping USD 21,492 at an auction in the US.

The noble award winner signed the two-sided letter dated December 5, 1919 as "Albert" on one side and "Papa" on the other.

"This is an exceptional handwritten letter offering details related to both Einstein's personal family life and his scientific legacy," according to the RR Auction house in the US.

The letter measures 9x11 inches and is in good condition.

In beginning of the letter, Einstein talks about the arrangement of divorce to his wife Mileva Maric and the education of his son Hans Albert.

"It seems that we are condemned to a kind of gypsy-life. Under the present circumstances I can understand you very well. I also prefer, of course, that Albert will not have to change schools. Completing school as soon as possible is not a good enough reason," he wrote.

On the reverse side Einstein pens a letter, signed "Papa," to his sons Hans and Eduard about their education, reminiscing about his own education, referring to his teachers Adolf Hurwitz and Ernst Amberg.

"I am pleased that you are taking lessons from Amberg. He is a very sympathetic man. He was an assistant to Hurwitz when I was a fledgling student; at that time I was tested by him in the Repetitozimmer. He was then quite young," Einstein wrote.

"Seiler was also an assistant in the Physics building when I was a student. I liked him less," Einstein wrote.